1. Field of the Invention
The present invention relates to a disc which insures a normal performance of an optical disc driver (ODD) by accounting for disc defects and a method of manufacturing the same, and more particularly, to a disc that is manufactured by quantifying defect factors affecting the ODD so as to insure the recording/reproducing capacity of the ODD and a method of manufacturing the same.
2. Description of the Related Art
The number of disc manufacturers has reached to hundreds throughout the world. Normally, each disc manufacturer follows general specifications based on disc standards and manufactures discs satisfying specific specifications which guarantee the quality of the discs. However, manufactured discs deviate from the specific specifications due to several factors, such as wear of a stamper used in a manufacturing of the discs, frequency of dye changes, and an injection temperature of the discs. In this case, an optical disc driver (ODD) will present a constant utilization error, i.e., the ODD does not normally record or read information on or from a disc using a pickup assembly. Therefore, defective discs which deviate from the specification are unavoidable due to problems associated with the manufacturing process. Since these problems directly affect the performances of the ODD, a method is needed to solve these problems.
However, it is very difficult and inefficient to improve the recording/reproducing capacity of an ODD with respect to a defective disc. That is, since the acquisition of a defective disc is possible while the continuous acquisition of the same type of defective disc is impossible, the continuous improvement of the reproducing capacity of an ODD has many limitations.
In addition, although continuous investigations and analyses of the acquired defective disc are needed, difficulties managing the research on this topic may cause secondary defect factors. In other words, when a surface of a disc is scratched, a user's fingerprints remains on the surface of the disc, and while the disc is repeatedly used, secondary defect factors, such as a deviation of an inner circumference of a spin hole, or the like, may additionally occur. Thus, it is difficult to accurately investigate the defect factors.
Furthermore, since frequently occurring defect factors have never been classified into types, an ODD manufacturer cannot but recall and analyze the defective disc and improve the reproducing capacity of the defective disc. Thus, taking comprehensive and systematic steps against defective discs has many limitations.
For the above-described reasons, a process of classifying disc defects into types and making the defective discs which satisfy normalized specifications based on a classified type is needed. Also, the recording/reproducing capacity of the ODD should not be affected when using the defective discs.
However, many disc manufacturers do not closely follow the normalized specification when manufacturing discs based on the formats specified in the orange book (CD-R), red book (CD-DA), and yellow book (CD-ROM). To manufacture defective discs in a predetermined range necessary to not affect the recording/reproduction capacity of the ODD using the defective discs, a stamper is made by considering instrumental characteristics of the defective discs. Here, the instrumental characteristics include an eccentricity, a deviation, a thickness, and a centroid, and are shown in Table 1 below.
TABLE 1NormalizedSpec of ManufacturedNoItemSpecDefective Disc1Eccentricity50μm280 μm Manufactured2Deviation0.3mm 1 mmconfined to3CentroidNo Spec1 gchanges in4Thickness1.2mm(1.2 + 0.3) mm–(1.2 − 0.1) mmphysical5Scratch 2 mmNormalizedformats6Fingerprint 75 μm as error7Dot 1 mmcorrectioncapacity
To manufacture a disc which satisfies the values presented in Table 1, the following items are changed when manufacturing a stamper. A disc is manufactured according to the eccentricity of the manufacturing specification so as to have the centroid deviate by 280 μm from the standardized value when cutting an inner hole after the stamper is manufactured. In addition, according to the deviation of the manufacturing specification, where the disc rotates, deviation components are created by varying the thickness of the inner hole after the stamper is manufactured. After the stamper is manufactured, scratches, fingerprints, and dots may be added to a surface of the disc.
The ODD may be regarded as having characteristics to account for a defective disc having the above-described instrumental characteristics, where the defective disc is reproduced in the ODD. However, stamper defects which occur during a stamper manufacturing and injection molding errors in the disc cause more problems than physical changes in the defective disc. Nevertheless, accurate and detailed data on defects of discs currently marketed do not exist, and discs manufactured based on defect characteristics are not supplied. Thus, it is difficult to stably and continuously improve the reproducing capacity of the ODD against the defect characteristics.